The invention relates to a device for transmitting and amplifying television signals, which device has an input terminal and an output terminal which can each be coupled to a distribution cable having a characteristic impedance R.sub.o, a first and a second branch being arranged in parallel with one another between said two terminals, which branches each comprise an amplifier, a high-pass filter being arranged between the input terminal and the amplifier of the first branch and a low-pass filter being arranged between the input terminal and the amplifier of the second branch in order to select a different frequency range for each of the two amplifiers.
Such a device is used particularly in cable television systems known as "MATV" or "CATV".
A device of the type defined in the opening paragraph is known from the document FR 1,106,667. In this known device the filters have been designed to provide two different frequency bands from 60 kHz to 4.1 MHz and from 5 MHz to 13 MHz, respectively. A similar arrangement referred to as a "split-band" arrangement is used in television for separately amplifying the VHF band (47-420 MHz) and the UHF band (470-860 MHz). It will be evident that a correct separation of frequencies which are spaced as closely as 420 MHz (upper limit of the VHF band) and 470 MHz (lower limit of the UHF band) requires a steep roll-off and high-order filters. Such filters are expensive and, in addition, they introduce substantial phase shifts, which may be annoying. Moreover, there is a gap between the frequency bands of each of the branches.
In order to obtain a continuous pass band it is, of course, possible to use a single amplifier covering the entire band from 47 to 860 MHz. However, a better performance as regards gain and distortion is obtained if the pass band is split into two parts because a satisfactory performance is easier to obtain as the pass band is narrower.
It is desired to have a device which provides a continuous pass band and has a better performance than a broadband amplifier. To achieve this, it may be envisaged to use a known device having two branches and to bring the cut-off frequencies of the two filters closer to one another or make them even coincide in order to reduce or to eliminate the discontinuity between the two parts of the pass band. Phase shifts in the filters then give rise to annoying irregularities of the amplitude and phase in the vicinity of the cut-off frequencies.